McLaren just teased the bespoke back end of the upcoming 675 Long Tail. A hopped up 650S sporting 40% more downforce and a new titanium crossover exhaust..if you're into that kind of thing

Power comes from a heavily-revised version of the 3.8-litre twin turbo V8 found in McLaren’s other cars. It gets lightweight components and new turbos here. A redesigned crossover exhaust system, the sound of which has been teased in the video above, has been formed from titanium.

The 675LT will be available as a coupe only, and will be fully revealed at the 2015 Geneva Motor Show on 3 March.

From the article:
The 675 LT was one of the most secret projects undertaken by McLaren. The hype around the sports series had worked in keeping this new car a surprise for everyone. We never saw or heard of this car before its unveil at the Geneva Motor Show. Even the test mule which was spotted outside the factory in Woking was disguised by using a 12C clam shell with only the two big exhausts giving out any hint of a possible new car. The teasers started coming out only a couple of weeks ago before its unveil and so this might be the first time a 675 LT has been caught going flat out on a camera.